Method for the preparation of 1,1,1,3,3-pentafluoropropene and 1,1,1,3,3-pentafluoropropane

ABSTRACT

A method for the production of 1,1,1,3,3-pentafluoropropene, and particularly to a method characterized by high conversion, yield and selectivity by contacting 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane with hydrogen in the presence of a metal-containing catalyst. The 1,1,1,3,3-pentafluoropropene then can be reacted with hydrogen in the presence of a metal-containing catalyst to produce 1,1,1,3,3-pentafluoropropane.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/286,150 filed Apr. 5, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for the production of1,1,1,3,3-pentafluoropropene, and particularly to a method characterizedby high conversion, yield and selectivity by contacting2,2-dichloro-1,1,1,3,3,3-hexafluoropropane with hydrogen in the presenceof a metal-containing catalyst. The 1,1,1,3,3-pentafluoropropene thencan be reacted with hydrogen in the presence of a metal-containingcatalyst to produce 1,1,1,3,3-pentafluoropropane.

2. Description of the Prior Art

Numerous methods are disclosed in the prior art for the preparation of1,1,1,3,3-pentafluoropropene (CF₃CH═CF₂). These methods vary widely, duein part to the different starting materials involved. The presentinvention provides a novel method for the preparation of1,1,1,3,3-pentafluoropropene via the treatment of2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (CF₃CCl₂CF₃) with hydrogen inthe presence of a catalyst. The reaction is characterized by highselectivity, conversion and yield, and offers significant economicadvantages over prior art preparations.

1,1,1,3,3-pentafluoropropene is a known chemical, and has found use as avaluable intermediate in the preparation of a variety of usefulcompounds. For example, as described in Bull. Acad. Sci., USSR Div.Chem. Sci. (Eng. Transl.), 1312 (1960) and in Chemical Abstracts122:132564, treatment of 1,1,1,3,3-pentafluoropropene with hydrogen inthe presence of a catalyst produces 1,1,1,3,3-pentafluoropropane, acompound useful as a solvent and blowing agent.

1,1,1,3,3-pentafluoropropene has been produced via thedehydrochlorination of 3-chloro-1,1,1,3,3-pentafluoropropane(CF₃CH₂CF₂Cl) with base as described in J. Amer. Chem. Soc. 68, 496(1946).

1,1,1,3,3-pentafluoropropene has been prepared via dehydrofluorinationof 1,1,1,3,3,3-hexafluoropropane with activated carbon or fluorinatedchromium oxide (JP 09067281; Chem Abs. 126:277171), and via treatment ofthe potassium salt of 2-trifluoromethyl-3,3,3-trifluoropropionic acidwith ethyl acetate as described in JP 08325179; Chem Abs. 126:143890).

1,1,1,3,3-pentafluoropropene has been prepared via dechlorination of2,3-dichloro-1,1,1,3,3-pentafluoropropane (CF₃CHClCF₂Cl) with hydrogenin the presence of a metal oxide catalyst as described in WO 9429251.

WO 9837043 describes the treatment of2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (CF₂CCl₂CF₃) with hydrogen inthe presence of a metal, metal halide or metal oxide catalyst supportedor alumina or a metal fluoride to produce a mixture of1,1,1,3,3-pentafluoropropene and 2-chloro-1,1,1,3,3-pentafluoropropene(CF₃CCl═CF₂).

Selectivity to CF₃CH═CF₂ is low, with substantial amounts of thechlorine-containing olefin CF₃CCl═CF₂ being co-produced in all cases.

Although the above described methods serve to produce1,1,1,3,3-pentafluoropropene, these prior art preparations arecharacterized by numerous disadvantages, including expensive rawmaterials, poor yields and poor selectivity which preclude their use ona commercial scale.

SUMMARY OF THE INVENTION

Briefly describing one aspect of the present invention, there isprovided a method for the production of 1,1,1,3,3-pentafluoropropenewhich includes reacting 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane andhydrogen at elevated temperature in the presence of a catalyst, andthereafter recovering the resulting 1,1,1,3,3-pentafluoropropene fromthe reaction mixture.

It is an object of the present invention to provide a method for theproduction of 1,1,1,3,3-pentafluoropropene from readily availablestarting materials. The starting material2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is itself a known compound,and is readily produced in high yields via the treatment of propane orpropene with chlorine and hydrogen fluoride as described in U.S. Pat.No. 5,057,634, hereby incorporated by reference.

A further object of this invention is to provide a method which has highconversion, high yield and high selectivity for the desired product,1,1,1,3,3-pentafluoropropene.

It is another object of the present invention to provide a method asdescribed which does not produce significant amounts of undesirableby-products.

Further objects and advantages of the present invention will be apparentfrom the description of the preferred embodiment which follows.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the preferred embodiment andspecific language will be used to describe the same. It willnevertheless be understood that no limitation of the scope of theinvention is thereby intended, such further modifications in theinvention, and such further applications of the principles of theinvention being contemplated as would normally occur to one skilled inthe art to which the invention relates.

The present invention is based upon the discovery that1,1,1,3,3-pentafluoropropene may be produced via the reaction of2,2-dichloro-1,1,1,3,3,3-hexafluoropropane and hydrogen at elevatedtemperatures in the presence of a catalyst. The conversions andselectivities for this process are very high, rendering the processapplicable to commercial scale production.

The basic method of the present invention involves the reaction of2,2-dichloro-1,1,1,3,3,3-hexafluoropropene and hydrogen in the presenceof a catalyst, preferably a metal-containing catalyst, according to thefollowing reaction (I):

CF₃CCl₂CF₃+2H₂→CF₃CH═CF₂+HF+2HCl  (I)

The reaction (I) is carried out by contacting2,2-dichloro-1,1,1,3,3,3-hexafluoropropane and hydrogen at elevatedtemperatures in the presence of a catalyst. Although preferred rangesfor contact times and molar ratios are stated hereafter, these rangesare not critical. In addition, the reaction may be carried out atambient or elevated pressures.

The temperature of the reaction is generally one which is high enough toprovide a desired amount and rate of conversion of the2,2-dichloro-1,1,1,3,3,3-hexafluoropropane, and low enough to avoiddeleterious effects such as the production of decomposition products.The reaction is therefore preferably carried out at a temperaturebetween about 100° C. and about 800° C. A more preferred range for thereaction is about 300° C. to about 500° C. It will be appreciated thatthe selected temperature for the reaction will depend in part on thecontact time employed, in general, the desired temperature for thereaction varying inversely with the contact time for the reaction.

The contact time will vary depending primarily upon the extent ofconversion desired and the temperature of the reaction. The appropriatecontact time will, in general, be inversely related to the temperatureof the reaction and directly related to the extent of conversion of2,2-dichloro-1,1,1,3,3,3-hexafluoropropane.

The reaction will typically be conducted as a continuous flow ofreactants through a heated reaction vessel in which heating of thereactants may be very rapidly effected. Under these circumstances, theresidence time of the reactants within the vessel is desirably betweenabout 0.1 second and 200 seconds, and is preferably about 10 seconds. Anadvantage of the reaction is that short contact times may be employed,thereby reducing the equipment size and cost associated with producing1,1,1,3,3-pentafluoropropene. The reactants may be preheated beforecombining or may be mixed and heated together as they pass through thevessel. Alternatively, the process may be carried out in a batch processwith contact time varying accordingly, although this is less preferred.The reaction also can be carried out in a multistage reactor, whereingradients in temperature, mole ratio, or both temperature and mole ratioare employed.

The molar ratio of the reactants may vary widely and is not critical tothe inventive method. Limitations on this ratio are more determined bypractical considerations. For example, a molar ratio of hydrogen to2,2-dichloro-1,1,1,3,3,3-hexafluoropropane which is extremely low willsimply require greater recycle of the2,2-dichloro-1,1,1,3,3,3-hexafluoropropane due to the low conversion,whereas a ratio that is very high will be wasteful of hydrogen. Apreferred range for the molar ratio of hydrogen to2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between about 0.1 and 30,with a ratio of about 2 to 8 being more preferred.

The invention provides a process for producing1,1,1,3,3-pentafluoropropene using2,2-dichloro-1,1,1,3,3,3-hexafluoropropane and involves the use ofadvantageous, preferred catalytic components employing a metal catalyst.The metal catalyst preferably is selected from the group consisting of ametal, metal oxide, metal halide, metal oxyhalide, and mixtures thereof,on a support, preferably a carbon support. Suitable metal-containingcomponents include metals such as Fe, Cu, Ni and Cr; halides such asFeCl₂, FeCl₃, CuF, CuCl, CuCl₂, CuClF, NiF₂, NiCl₂, NiClF, CrF₃, CrFCl₂,CrF₂Cl; oxides such as CuO, NiO, and Cr₂O₃; and/or oxyhalides such ascopper oxyfluoride and chromium oxyfluoride.

The catalysts of this invention may contain other components, some ofwhich improve the activity and/or useful life of the catalyst. Preferredcatalysts include catalysts which are promoted with compounds ofmolybdenum, vanadium, tungsten, silver, iron, potassium, cesium,rubidium, barium or combinations thereof.

The catalyst preferably is supported on an active carbon support. Theactive carbon can take the form of any of the numerous active carbonsavailable commercially, for example the commercial guide productproduced by Takeda. Typically the solid catalyst is packed into areactor tube, although fluidized bed technology can also be employed.

The process of the present invention has several advantageous aspects inaddition to those described above. The reaction involves readilyobtainable reactants, namely 2,2-dichloro-1,1,1,3,3,3-hexafluoropropaneand hydrogen. The reaction product is the desired1,1,1,3,3-pentafluoropropene. Very high yields of the desired productare ultimately attainable, and therefore the reaction is efficient inits use of the reactants without producing miscellaneous undesirable byproducts, and is a highly efficient and advantageous method for theproduction of 1,1,1,3,3-pentafluoropropene.

The 1,1,3,3-pentafluoropropene product is separated from the productmixture via conventional means, for example distillation. The reactionstream can be treated with water or an aqueous solution to facilitateremoval of inorganic acids, and the organic portion of the productmixture can be subjected to fractional distillation to allow recovery ofthe product and recycle of the starting material2,2-dichloro-1,1,1,3,3,3-hexafluoropropene.

The efficacy of the process of the present invention is illustrated bythe following specific examples. The following specific embodiments areto be construed as illustrative, and not as constraining the remainderof the disclosure in any fashion whatsoever.

EXAMPLE 1 Catalyst Preparation

NiO/active carbon: Nickel (II) nitrate hexahydrate (1.9 moles) wasdissolved in distilled water (250 mL). The solution was then added to550 g of Takeda active carbon pellets, the catalyst dried with nitrogenand activated at 450° C.

NiO/CuO/active carbon: A mixture of nickel (II) nitrate hexahydrate(0.95 mole) and copper (II) nitrate hemipentahydrate (0.95 mole) wasdissolved in distilled water (320 mL). The solution was added to 500 gof active carbon pellets. The catalyst was then dried with nitrogen andactivated at 450° C.

CuCl₂/active carbon: Copper (II) chloride dihydrate (1.9 moles) wasdissolved in distilled water (325 mL). The solution was then added to550 g of active carbon pellets. The catalyst was then dried withnitrogen and activated at 350° C. with hydrogen.

EXAMPLE 2 Preparation of 1,1,1,3,3-pentafluoropropene

A 10 inch diameter by 24 inch long Inconel pipe was packed with thedesired catalyst and heated with an electric heater. A 0.5 inch by 8inch empty pipe heated by electrical heating tape was connected to theinlet of the reactor and served as a vaporizer. A water scrubber and amolecular sieve drier were attached to the reactor outlet and wereemployed to remove acids from the product mixture and to dry the organicproducts. Hydrogen gas (200 mL/min) and liquid2,2-dichloro-1,1,1,3,3,3-hexafluoropropane (0.3 mL/min) were fed intothe vaporizer and the vaporized mixture passed through the reactor. Theproduct mixture was washed with water, dried and collected. Reactionresults are summarized in Table 1; the conversion of2,2-dichloro-1,1,1,3,3,3-hexafluoropropane was essentially quantitative.

TABLE 1 Preparation of 1,1,1,3,3-pentafluoropropene Catalyst Reaction T(° C.) % Selectivity CF₃CH═CH₂ NiO/CuO 350 89 NiO/CuO 500 90 NiO 350 81NiO 425 80 CuCl₂ 350 90

EXAMPLE 3 Preparation of 1,1,1,3,3-pentafluoropropane

A 0.5 inch by 24 inch stainless steel pipe was packed with a catalystconsisting of 0.5% Pd on alumina pellets and heated with an electricheater. A mixture of hydrogen (128 mL/min) and1,1,1,3,3-pentafluoropropene, prepared as in Example 2, was fed to thereactor. The product stream was washed with water to remove acids andcollected. Results are shown in Table 2.

TABLE 2 Preparation of 1,1,1,3,3-pentafluoropropane % SelectivityReaction T (° C.) Lights CF₃CH₂CF₂H Heavies 50 2.7 94.4 2.9 35 2.6 95.02.4

While the invention has been described in detail in the foregoingdescription, the same is to be considered as illustrative and notrestrictive in character, it being understood that only the preferredembodiment has been described and that all changes and modificationsthat come within the spirit of the invention are desired to beprotected.

What is claimed is:
 1. A method for the production of1,1,1,3,3-pentafluoropropene which comprises contacting2,2-dichloro-1,1,1,3,3,3-hexafluoropropane with hydrogen in the presenceof a metal-containing catalyst carried by a carbon support, at atemperature in the range of about 350° C. to about 800° C., andrecovering the 1,1,1,3,3-pentafluoropropene from the resulting reactionproduct, wherein the metal-containing catalyst carried by a carbonsupport is selected from the group consisting of a metal, metal halide,metal oxide, metal oxyhalide and combinations thereof, wherein the metalof the catalyst is selected from the group consisting of Fe, Cu, Ni andCr.
 2. The method of claim 1, wherein the carbon catalyst support isactivated carbon.
 3. The method of claim 1, wherein said contacting iscarried out in a reactor for a period of time between about 0.1 and 60seconds.
 4. The method of claim 1, wherein the molar ratio of hydrogento 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between about 0.1 andabout
 30. 5. The method of claim 4, wherein the molar ratio of hydrogento 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between about 2 to 8.6. The method of claim 1, wherein the reaction temperature is from about350° C. to about 500° C.
 7. The method of claim 1, wherein the reactionpressure is in the range from ambient to about 450 psi.
 8. The method ofclaim 7, wherein the reaction pressure is in the range of ambient toabout 200 psi.
 9. A method for the production of1,1,1,3,3-pentafluoropropane comprising (1) contacting2,2-dichloro-1,1,1,3,3,3-hexafluoropropane with hydrogen in the presenceof a metal-containing catalyst carried by a carbon support, at atemperature in the range of about 350° C. to about 800°C., andrecovering 1,1,1,3,3-pentafluoropropene from the resulting reactionproduct, wherein the metal-containing catalyst carried by a carbonsupport is selected from the group consisting of a metal, metal halide,metal oxide, metal oxyhalide and combinations thereof, wherein the metalof the catalyst is selected from the group consisting of Fe, Cu, Ni andCr, and (2) contacting the recovered 1,1,1,3,3-pentafluoropropene withhydrogen in the presence of a metal-containing catalyst to produce1,1,1,3,3-pentafluoropropane.
 10. The method of claim 9, wherein themetal-containing catalyst is selected from the group consisting of ametal, metal halide, metal oxide, metal oxyhalide and combinationsthereof.
 11. The method of claim 10, wherein the carbon catalyst supportis activated carbon.
 12. The method of claim 9, wherein the molar ratioof hydrogen to 2,2,-dichloro-1,1,1,3,3,3-hexafluoropropane is between0.1 and about
 30. 13. The method of claim 9, wherein the molar ratio ofhydrogen to 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between 2 to8.
 14. The method of claim 9, wherein the reaction temperature is fromabout 350° C. to about 500° C. and the pressure is from ambient to about450 psi.
 15. A method for the production of1,1,1,3,3-pentafluoropropene, with a selectivity of at least 80%, whichcomprises contacting 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane withhydrogen in the presence of a metal-containing catalyst carried by acarbon support, at a temperature in the range of about 350° C. to about800° C., and recovering the 1,1,1,3,3-pentafluoropropene from theresulting reaction product, wherein the metal-containing catalystcarried by a carbon support is selected from the group consisting of ametal, metal halide, metal oxide, metal oxyhalide and combinationsthereof, wherein the metal of the catalyst is selected from the groupconsisting of Cu, Ni.
 16. The method of claim 15, wherein the carboncatalyst support is activated carbon.
 17. The method of claim 15,wherein said contacting is carried out in a reactor for a period of timebetween about 0.1 and 60 seconds.
 18. The method of claim 15, whereinthe molar ratio of hydrogen to2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between about 0.1 andabout
 30. 19. The method of claim 18, wherein the molar ratio ofhydrogen to 2,2-dichloro-1,1,1,3,3,3-hexafluoropropane is between about2 to
 8. 20. The method of claim 15, wherein the reaction temperature isfrom about 350° C. to about 500° C.
 21. The method of claim 15, whereinthe reaction pressure is in the range from ambient to about 450 psi. 22.The method of claim 21, wherein the reaction pressure is in the range ofambient to about 200 psi.
 23. The method of claim 15, wherein theselectivity is in the range of 80-90%.
 24. A method for the productionof 1,1,1,3,3-pentafluoropropane, with a selectivity of at least 75.52%,comprising (1) contacting 2,2-dichloro-1,1,1,3,3,3-hexafluoropropanewith hydrogen in the presence of a metal-containing catalyst carried bya carbon support, at a temperature in the range of about 350° C. toabout 800° C., and recovering 1,1,1,3,3-pentafluoropropene from theresulting reaction product, wherein the metal-containing catalystcarried by a carbon support is selected from the group consisting of ametal, metal halide, metal oxide, metal oxyhalide and combinationsthereof, wherein the metal of the catalyst is selected from the groupconsisting of Fe, Cu, Ni and Cr, and (2) contacting the recovered1,1,1,3,3-pentafluoropropene with hydrogen in the presence of ametal-containing catalyst to produce 1,1,1,3,3-pentafluoropropane. 25.The method of claim 24, wherein the metal-containing catalyst isselected from the group consisting of a metal, metal halide, metaloxide, metal oxyhalide and combinations thereof.
 26. The method of claim25, wherein the carbon catalyst support is activated carbon.
 27. Themethod of claim 24, wherein the reaction temperature is from about 350°C. to about 500° C.